Etching machine paddle



y 11, 1967 M. H. FISHABER ETAL 3,330,212

BTCHING MACHINE PADDLE Filed Oct. 24, 1965 INVENTORS. Marv/n H,F/lshaber John 0. H/ckenson 97' TORNE Y United States Patent 3,330,212ETCHING MACHINE PADDLE Marvin H. Fishaber, Saginaw, and John D.Hickerson,

Midland, Mich., assignors to The Dow Chemical Company, Midland, Mich, acorporation of Delaware Filed Oct. 24, 1965, Ser. No. 504,965 Claims.(Cl. 10384) This invention relates to etching machines and moreparticularly concerns a novel paddle device, especially useful in curvedplate powderless etching, and adapted to be used in curved plate etchingmachines.

Present commercially available curved plate paddle type etching machinessplash the etchant substantially perpendicular to the plate or cylinderaxis, while said cylinder rotates with periodic reversals. As thecylinder rotates in this manner and etching of the metal occurs, theetchant is naturally caused to flow in currents over the plate in thedirection of curvature. This commonly results in severe tailing or inother words, the formation of excessively elongated image side walls inthe direction of curvature. Transversely, the image shoulders areessentially perpendicular to the face of the plate and in many casessevere undercutting or undermining of the image may result.

It has been found beneficial in the powderless etching of curved platesor cylinders to impinge or splash the etchant solution in other than aperpendicular direction onto the plate during rotation relative to thecylinder axis.

The primary object of the present invention is to provide an improvedpaddle device for use in a curved plate powderless etching machine.

Another object of the invention is to provide a novel paddle forimpinging etchant in a powderless etching machine onto a curved segmentor cylinder at an angle of less than 90 degress to the axis of saidcylinder.

Another object of the invention is to provide such a paddle which willimpinge etchant onto a rotating plate in a sequential cycle ofalternately opposing angles of less than 90 degrees to the plate orcylinder axis.

The invention will be more readily understood from the followingdetailed description and the accompanying drawing wherein:

FIG. 1 is an isometric view, partially cut away of an etching machineutilizing the novel paddle of the present invention wherein two paddlesof one embodiment of the novel paddle device are disposed within themachine in a spaced relationship to each other on opposite longitudinalsides of a rotating curved plate held by a cylindrical plate holder ormandrel.

FIG. 2 is a side view of one of a novel paddle device similar to thatshown in FIG. 1 except that the arrays of vanes on the fins thereof areoppositely directed.

FIG. 3 is an end view of the novel paddle device shown in FIG. 1.

With reference to the drawing and specifically to FIG. 1 the novelpaddle 8 of the present invention comprises in general a plurality oflongitudinally disposed outwardly extended fin members 10 around orforming an axle 12 on which to rotate. Each such fin 10 is providedalong its lip or outer longitudinal portion 14 a longitudinal array 16of parallel spaced directional vanes 18, with each set of vanes beingpreferably alternately directionally opposed. Preferably, the lip orouter longitudinal portion 14 of each fin 10 wil be angled in a commondirection (toward the plate) so as to scoop-11p or skim etchant from thesupply thereof at the bottom of the machine and impinge same against therotating plate. These angles should not preferably exceed about 60.

FIG. 2 in side elevation shows in a more clear manner the alternatingdirectional attitude of the vanes 18 on the various fins 10, and FIG. 3shows an end view of the 3,330,212 Patented July 11, 1967 paddle and thecommon angulus disposition of the lip of each fin.

While there is no actual limitation as to the number of fins comprisingthe present novel paddle, a preferred and convenient number has beenfound to be four (4). In any event, the fins should be reasonably andequally spaced apart. It is preferred to have the direction of the vaneson the lip of alternate fins as opposing so as to impinge etchant firstin one direction and then in another. The direction of the vanes,however, may be cycled in most any manner to obtain the desired etchingeffect as heretofore described.

In order that the present device be resistant to attack itself by thevarious etching solutions, most of which contain appreciable amounts ofmineral acids such as nitric and hydrochloric acids, the device shouldbe fabricated, for example, of stainless steel or other acidetch-resistant material.

When employing the present novel invention in an etching machine it ismanifest that support and drive means (not shown in drawing) must beprovided for operation thereof. In practice it is hereby intended thatthe present novel device be constructed as to render it adaptable to asimple substitution for conventional paddles in present conventionalmachines.

With this novel paddle when the paddle 8 is caused to rotate in anetching machine 20 and contact a level 22 of etching liquid 24- in themachine in conjunction with vanes or alternate fins it will operate tocyclically impinge (not shown) etchant at an angle of less than onto arotating plate 26 to be etched, first in one direction then in anotheropposing direction. Splashing or impinging etchant in this directionalmanner produces a more uniform fiow of said etchant around the sidewalls of an image on the plate as it rotates, thus greatly reducingelongated image shoulders in the direction of curvature and undercuttingin the transverse direction.

Among the advantages of the invention are that a significant improvementin shoulder uniformity of an etched image is obtained which allowsdeeper etching without undercutting of the image in the transversedirection of the curvature. Cleaner edges of the highlight dot areas inthe direction of curvature are also obtained. Moreover, the paddles ofthe present invention can also be used for high quality etching of flatplates. Thus, if a machine has two plate movement mechanisms (i.e., onedetachable means for movement of a fiat plate and a separate means formovement of a cylindrical or curved plate) the same machine can beconveniently used for etching either kind of printing plate. Overall, ageneral improvement in the appearance and quality of the etched curvedplate is obtained by means of the present invention.

The terms curved plate or curved segment as used herein refers broadlyto curved surfaces in general use for engraving and printing andinclude, for example, magnesium or zinc plate, sheet, thin wrap-aroundsheet, extruded tubing, extruded cylinders, impact extruded cans, thinwrap-around foil, and the like.

The following example serves to further illustrate the present inventionbut is not to be construed as limiting the invention thereto.

Example of invention A standard model M-32 Master brand powderlessetching machine adapted for curved plates was modified by removing theconventional paddles (2 in number) and replacing these with oneembodiment of present novel paddles substantially as shown in theappended drawing. The machine so-modified was then charged with 77liters of a powderless etc-hing bath comprising 10 volume percent of 42B. nitric acid, 0.685 percent by volume of monochlorododecyldiphenyloxide sodium sulfonate; 0.15

percent by weight of a monocarboxylic acid; 2.5 volume percent of amixture of aromatic solvents of Panasol AN-1, Solvesso 150, and dodecylbenzene; the balance of the bath being essentially water.

a The bath was adjusted to a temperature within the range of fromabont70 to 73 F. An etchable combinationcurvedplate or segment 8 inches indiameter exhibiting line and halftone image areas was clamped to themandrel in the machine and rotated at about 30 to 60 'r.p.m., thedirection of rotation being reversed about every seconds. Vanes on thefins of the paddles were longitudinal axis of the paddle. The paddles inthe machine were also rotated at from about 300 to about 380 r.p.m. soas to splash etchant bath against the plate. The 1 machine was operatedin this manner 'for about 8-10 minutes, whereupon, the machine wasstopped and the etched plate removed and rinsed. The depth of etchvaried from 18 to 21 thousandths of an inch. Because of the angle of thevanes on the paddle fins the angle at which the etchant impinged theplate during the etching 'operation was substantially non-perpendicularto the longitudinal axis of the plate.

As a quantitative measurement and indication of the quality of etching,an average angle of difference was obtained by computing the imageshoulder angle in the direction of curvature and also in the transversedirection and determining the average difference over a number ofmeasurements on the plate. The angle of difference so-determined wasabout 18, which is very acalternately set at opposing angles of about 30to the a ceptable and quite desirable. This showed that an image a .dot,for example, had a substantially uniform shoulder.

Comparative example The procedure of the above example was repeatedunder the same conditions except that the conventional standard paddleswere employed in the M-32 machine. The etchant impinged the plateperpendicularly. Again the angle of difference of the image shoulder wasmeasured and computed, but was found to be about 34. This indicates thatthe image shoulder "in the direction of curvature was undesirable inthat it was excessively elongated compared to the image shoulder in thetrans- V verse direction and therefore the plate was of only limited 7or marginal use for printing.

when, for example,

used therein provides an outstanding increase in quality of the etchedplate by substantially reducing the elonga tion of the image shoulder"in the direction of curvature.

The present invention can be modified or changed without departing fromthe spirit or scope thereof, and it is understood that the presentinvention is only limited as defined in the appended claims.

We claim: 7 a 4 1. A rotatable paddle for use in curved plate etchingmachines comprising: a plurality of fin members each coupled along onelongitudinal edge to form aycommon axle, the outer longitudinal portion'of each fin carrying an array of parallel, spaced, directional vanes,said vanes being disposed at an angle of less than to the longitudinalaxis of the paddle and at least two of said arrays of vanes beingdirectionally opposed. i

2. The paddle of claim 1 wherein uniformly circumferentially spacedapart.

3. The paddle of claim 1 wherein there are jacent fins.-

4. The paddleof claim portion of each fin is angled at less than 90"tothe trans:

verse axis of said fin in the direction in which said paddle would berotated.

5. The paddle of claim 1 wherein the vanes are angled with respect tothe longitudinal axis of the paddle approximately 30.

7 References Cited UNITED STATES PATENTS 7 DONLEY I. STOCKING, PrimaryExaminer.

Clearly, the novel paddles of the present invention 7 H. F. RADUAZO,Assistant Examiner.

substituted in a conventional curved plate etching machines forthestandard paddles normally he fin members are four formly spaced finmembers, the array of vanes on each fin being directionally opposed tothe vanesof the ad- 1 wherein the outer longitudinal i

1. A ROTATABLE PADDLE FOR USE IN CURVED PLATE ETCHING MACHINESCOMRPISING: A PLURALITY OF FIN MEMBERS EACH COUPLED ALONG ONELONGITUDINAL EDGE TO FORM A COMMON AXLE, THE OUTER LONGITUDINAL PORTIONOF EACH FIN CARRYING AN ARRAY OF PARALLEL, SPACED, DIRECTIONAL VANES,SAID VANES BEING DISPOSED AT AN ANGLE OF LESS THAN 90* TO THELONGITUDINAL AXIS OF THE PADDLE AND AT LEAST TWO OF SAID ARRAYS OF VANESBEING DIRECTIONALLY OPPOSED.